The present invention relates to a method of homogenization of a pressurised liqueform emulsion, in which the liquid is caused to pass at least two concentrically placed homogenization gaps.
Homogenization is an industrial process which has long been employed and whose purpose is, in a fat emulsion such as, for example, milk, to shear or split the largest fat globules into smaller fat globules and by such means stabilize the fat emulsion. For, for example, milk, this implies that cream-clotting is prevented, and the vast majority of all consumer milk today is homogenized.
Homogenization normally takes place by mechanical processing, such that the fat emulsion, which is at a high infeed pressure, is forced at high speed to pass through a very narrow gap where the fat globules of the fat emulsion are broken up as a result of the turbulence which occurs at high speeds and by means of cavitation bubbles which implode in the liquid. The process takes place during a very short period of time and what happens during this brief period is that the speed of the fat emulsion on its passage increases while the pressure drops, which results in the liquid coming to the boil.
A homogenizer substantially consists of a large piston pump which gives high pressure, and a counter-pressure device where the homogenization proper takes place. The counter-pressure device, the homogenizer valve in turn consists of a pressurised, resilient valve cone, a valve seat and a valve housing which surrounds the valve cone and the valve seat. The valve cone and the valve seat are normally rotation-symmetric and are disposed such that between these parts, a radial throttle occurs which constitutes a homogenization gap. The height, width and length of the gap determine the volume at which the homogenization takes place. This volume must be as slight as possible in order to obtain an efficient homogenization. The gap height is reduced at an elevated pressure on the liquid which is to be homogenized, at the same time as a greater flow entails that the gap height is increased.
It is often desirable today to employ a lower pressure on the liquid, at the same time as the intention is to increase the flow volume. This implies that a longer homogenization gap is needed. Various methods for lengthening the homogenization gap are known from the patent literature. Swedish Patent Application SE 9701504-4 discloses a homogenization valve in which a number of homogenization gaps are concentrically disposed, which thereby gives an increased length of the homogenization gap.
Most generally, it is insufficient merely to extend the homogenization gap. In order to obtain as efficient homogenization as possible, where all fat globules, for example in milk, are sheared or split into such small fat globules that a stable emulsion is obtained. This problem has most generally been solved by carrying out the homogenization process in several stages.
U.S. Pat. No. 5,482,369 discloses a further method of obtaining an efficient homogenization. This method takes as its point of departure that the component parts or phases of the emulsion, for example water and fat which are both under pressure, are caused to pass through two opposed nozzles so that the two jets meet at high speed. The two nozzles are fixed and have a very narrow gap where the two liquids are to pass Milk, which already from the outset consists of a mixed, unstable fat emulsion which may contain naturally occurring particles would, in such a homogenizer, rapidly block the narrow gaps of the nozzles and render the process unusable.
One object of the present invention is to realise a homogenization gap which is of optimum design and is controllable for desired flow and pressure, at the same time as a more efficient and improved homogenization is obtained by utilising the speed at which the liquid passes the homogenization gap.
This and other objects have been attained according to the present invention in that the method of homogenization of the type described by way of introduction has been given the characterizing feature that the liquid, when passing out from one of the homogenization gaps at high speed and in a restricted space, meets the liquid out from one or more of the other homogenization gaps.
Preferred embodiments of the present invention have further been given the characterizing features as set forth in the appended subclaims.